Own Occupation Disability Insurance is a DI policy that will pay the insured person if they cannot perform their "own occupation" due to being disabled. The definition in the contract goes something like this:
"The inability to perform the material and substantial duties of your regular occupation, with the insurance company considering your occupation to be the occupation you had at the time of becoming disabled, and the company will pay the claim even if you are able to work in another capacity."
E.g. If you are a rocket scientist who is unable to remember complicated formulas due to progressing MS, you can still receive your disability benefit despite being able to work as a data entry person.
"The inability to perform the material and substantial duties of your regular occupation, with the insurance company considering your occupation to be the occupation you had at the time of becoming disabled, and the company will pay the claim even if you are able to work in another capacity."
E.g. If you are a rocket scientist who is unable to remember complicated formulas due to progressing MS, you can still receive your disability benefit despite being able to work as a data entry person.